Matter and Elements

Matter takes up space and has weight when matter is subjected to gravity. Matter consists of extremely tiny particles grouped together to form atoms. There are approximately 100 different naturally, occurring atoms called elements. An element is a substance that cannot be decomposed any further by chemical action. Most elements have been found in nature. The following are examples of some of the natural elements: copper, lead, iron, gold and silver. Elements can be combined to make compounds. The atom is the smallest particle of an element that still has the same characteristics as the element. Atom is the Greek word meaning a particle too small to be subdivided.

Even though each atom in a piece of material tends to hold together as a unit, there's actually a lot of empty space between the electrons and the cluster of protons and neutrons residing in the middle.

In any atom, the protons and neutrons are very tightly bound together, which is an important quality. The tightly-bound clump of protons and neutrons in the center of the atom is called the nucleus, and the number of protons in an atom's nucleus determines its elemental identity:

 
Atoms

Although an atom has never been seen, the structure fits evidence that has been measured accurately. The size and electric charge of the invisible particles in an atom are indicated, by how much the atoms are deflected by known forces. The present atomic model, with a nucleus at the center was proposed by Niels Bohr in 1913. The atomic model is patterned after the solar system with the sun at the center and the planets revolving around it.